Burglar alarm system



Oct. 21, 1952 A, KRUEGER BURGLAR ALARM SYSTEM Filed Sept. 21, 1946 NVEJvTOkg afl uqusb @Hue M41: 6%"

Patented Oct. 21, 1952 UNITED STATES PATENT OFFICE BURGLAR'ALARM SYSTEM August Krueger, Chicago,l Ill.

Application September 21, 1946, Serial No. 698,499

2 Claims.

The present invention relates to improvements inburglar alarm systems for doors.

One'of the objects of the invention is to provide a burglar alarm system` which is associated with a conventional door lock, and which-will emit an alarm signal if the door'knob or handle is tampered with when the door is locked.

Ail. further object is to provide a'burglar alarm system comprising a simple and inexpensive controlswitch unit which is adapted to be operatively associated with the keeper plate of the door lock, and which includes a series of switches operable respectively by the spring latch and sliding bolt of the lock to control the alarm-signal.

Another and more specic object is to provide a burglar alarm system of the foregoing character having two switches connected in series in an electric alarm circuit, with one switch normally closed and adapted to be openedby the spring latch when extended, and with the other switch normally open and adapted to be closed by the sliding bolt when extended, whereby when the door is locked, retraction of the latch will close the alarm circuit.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings:

Fig. l is a fragmentary perspective View of a burglar lalarm with a schematic representation of 'the alarm circuit, embodying the features of the present invention;

Fig. 2 is a fragmentary vertical sectional View through the control switch unit of the burglar alarm system;

Fig. 3 is a view similar to Fig. 2, but illustrating a modified form of the invention adapted particularly for automobile doors;

Fig. 4 isa transverse vertical sectional view taken along line 4 4 of Fig. 3;

Fig. 5 is a diagrammatic illustration of an electricalarm and ignition circuit, including the switch unit illustrated in Figs. 3 and 4.

Referring more particularly to the drawings, the burglar alarm system of Figs. l and 2, constituting one exemplary embodiment of the invention, in this instance primarily adapted for house doors, is shown in operating association with a conventional swinging door 6 mounted within a frame 'I. The door 6 is provided with a conventional lock 8, the details of which per se formno part of the present invention and hence are not fully disclosed. It is'suficient to state that the lock 8 comprises a suitable frame 9 secured Within the outer swinging edge of the doorA 6, and enclosing a normally extended spring actuated latch Ill retractable by means of a door knob II, and a rectangular sliding bolt I2 shiftable into either projected or retracted position by means of a key (not shown).

`A keeper plate I3 is inset within and rigidly secured to the inside face of a door jamb I4,

forming part of the door frame 'I. More particularly, the plate I3 is formed fwith two vertically spaced rectangular openings I5 and I 6 adapted respectively to receive the latch IIJ and bolt I2 when the door 6 isv closed. Normally, a recess I'I is formed in the jamb I4 back yofthe plate I3 to provide clearance for the latch III and bolt I2.

The prese-nt burglar alarm system comprises a self-*contained control switch vunit I8 which is associated with the plateIS for actuation bythe latch I0 and bolt I2, and which is operatively connected in a suitable electric alarm circuit. The preferred arrangement is such that the alarm circuit is disabled when the bolt I2 isl retracted to unlock the door, and is conditioned for operation when the bolt is projected through the opening kI6 -so vas to emit an alarm signal in the event and whenever the latch I0 is retracted by rotation rof the hand knob II. More particularly, the switch unit I8 comprises .a vertical elongatedplate or other suitablesupport I9 ,ofelec trical insulating material connected at opposite ends by inwardly extending brackets 20 to the inner face of the plate I3.

Mounted in the upper portion of the support I9, in alignment with the uppermost `opening I5, for actuation by the latch I0, is a normally closed switch 2| having xed spaced button contacts22, and a movable disc contact 23 adapted to bridge the xed contacts. The contact 23 is xed on an actuating stem 24 extending slidably through the support I9. A circular abutment head or ange 25 is xed .on the forward end of the stem 24, and is disposed for end engagement -by latch I0. A .coil compression spring 26 about the stem 24 between thesupport I9 and the head 25 tends `to urge the contact 23 toward and into bridgingengagement with vthe contacts 22. Thus, the switch 2l will close when the knob II is rotated to retract the spring latchA Illas, for example, when opening thedoor 6, and will ybe opened when the knob is released to release the latch for engagement with the head 25 .if the door is in closed position.

A normally open switchv2`l is mounted on the lower portion of the support I9 in position to be closed by the sliding bolt I2, whichacts as a movable bridge contact. The switch 21 comprises two spaced parallel spring contacts 28 and 29, each preferably in the form of a bowed strap or leaf secured at one xed end by means of a rivet 30 to the support I9, and disposed -at the other free end partiallyacross the opening I6 in the ,path ofthe bolt I2. Thus, when the door 6 is in closed positionI the switch 21 will be closed by the bolt I 2 when the door is locked to rcondition the alarm circuit for operation, and will be opened when the door is unlocked to disable the alarm circuit.

The .electric alarm circuit maybe of any desired character. In the present arrangement; the

control switches 2| and 21 are connected therein in series, a line 3| leading from one of the contacts 22 to the spring contact 28. The other of the contacts 22 of the switch 2| is connected through a line 32 to an alarm signal device which may be of any suitable character, and which is shown as an electrically operated bell 33. Thence the circuit continues through a line 34 to one terminal of a suitable source of electric current, such as a storage battery or service main indicated at 35. The other terminal of the source 35 is connected through a line 3S to the spring contact 2B of the switch 27 to complete the circuit. Preferably, the switch unit is enclosed in a housing 38 tted within the recess Il. It will be obvious that the bell 33 will be operated to give an alarm signal when both switches 2| and 21 are closed, and that the switches will both be closed when the door is locked to project the bolt I2, and the handle is then turned to retract the latch lil in any attempt to open the locked door.

If desired, a hand switch S may be connected in the circuit in parallel with the switch 21. When the switch S is closed, the alarm circuit will be marily for use in automobile doors and illustrated c' in Figs. 3, 4 and 5, is generally similar to that oi Figs l and 2, and corresponding parts thereof are, therefore, identied by the same reference numerals distinguished by the letter a. In

this instance, the leaf spring contacts 28a. and 29a I are disposed on the opposite side of the support iSa, and instead of being bridged directly by the bolt |2a are adapted to be closed by a movable contact 3l operable by the bolt |20.. The contact 31 is iixed on a stem 39 extending slidably through the support ISa, and having a collar or flange 4D on the forward end engageable by the bolt |2a. A coil compression spring 4| about the bolt between the support i9@ and the collar 40 tends to urge the contact 37 out of engagement with the spring contacts 28a. and 29a and into engagement across two other spaced fixed contacts 42 on the rear of the support. One of the contacts 42 is connected through a line 43 to the line 34a. The

other of the contacts 42 is connected through a line 44, ignition switch l5 and a line 46 to the L ignition plug system 4'! of an automotive engine, in turn connected through a line 48 to the line Sa to complete the ignition circuit.

In operation, when the car door is unlocked, the a bolt |2a will be retracted to open the alarm circuit at the contacts 28a andv29a and to close the ignition circuit at the contacts 42. As a result, the circuit through the alarm signal device 33a is interrupted to disable the burglar alarm system. At the same time, the ignition circuit is conditioned for operation so that the engine can be started when the ignition switch 45 is closed. When the automobile door is locked, the bolt |2a will be projected into the switch unit lila to open the contacts 42, thereby disabling the ignition circuit, and to close the contacts 28a and 29a by the contact 3l', thereby conditioning the burglar alarm circuit, Under this condition, the spring latch ma when projected through the opening |5o in the plate i3d will interrupt the alarm circuit. However', if the door handle should be actuated in an attempt to open the locked door, the switch 2|a will close to eiect energization of the signal device 33a.

It will be evident that I have provided a new and improved burglar alarm system adapted for various types of doors, and capable of simple operative assembly with conventional door locks of the double bolt type. As long as the door is unlocked, the alarm system is disabled. However, whenever the door is locked, tampering with the knob or handle will cause the signal device to give an alarm.

I claim as my invention:

l, A combination burglar alarm and ignition system for automobile d-oor locks of the type having a -handle actuated spring latch and a key operated sliding bolt, said system comprising, in combination with a plate for mounting in the door frame and formed to receive said latch and said bolt, an alarm circuit having an alarm device therein, an ignition circuit, said circuits including a common source of current, an insulating support adapted to be mounted in spaced relation back of said plate, a normally closed switch having two terminals connected in series in said valarm circuit, said switch being mounted on said support for engagement by said latch to open the switch when projected through said plate, a second switch mounted on said support in position for operation by said bolt and having a first pair of terminals in series in said alarm circuit, a second pair of terminals in series in said ignition circuit, and having an actuator including two mechanically coupled but electrically insulated contact members for alternatively connecting the terminals of said pairs, said actuator being normally biased so that one of said contact members connects said second pair of terminals and being operable upon engagement thereof by said bolt upon its projection through said plate into locking position to open the connection between said second pair of terminals and connect said First pair of terminals by engagement thereof by the other of said contact members, whereby retraction of said latch will cause said device to emit an alarm signal.

2. A combination burglar alarm and ignition system for automobile door locks having a spring latch and a locking bolt comprising, in combination, an alarm circuit including an alarm signal device, an engine ignition circuit, and a control switch unit comprising two switches in said alarm circuit operable respectively by said latch and bolt to disable said alarm circuit when said door `is unlocked, to condition said alarm circuit for operation when said door is locked and said latch is in normal position, and to close said alarm circuit when said door is locked and said latch is moved out of normal position, and a third switch in said ignition circuit mechanically coupled with one of said two switches and operable to close when said bolt isA withdrawn to unlock the door and to open when said one switch is closed upon loci/:ing of the door.

AUGUST KRUEGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Date. 

